The present invention relates to a motion-picture camera. More particularly, this invention concerns such a camera provided with an automatic fade out.
In a motion picture camera the film is usually advanced by an electric motor that is connected across a power supply by means of a release switch that is closed when film is to be exposed. This switch is, for example provided as a trigger on a grip of the camera.
It is also known in such devices to provide an automatic exposure control, normally comprised of a photosensitive element provided in the camera behind the diaphragm and connected to an electric drive mechanism that increases the lens or diaphragm aperture when insufficient light is falling on it and decreases when too much light is falling on it. Such an automatic control is set for the exposure time, which is typically the same in movie cameras, and the ASA or DIN rating of the film.
It is also known to provide such a camera with a circuit making it possible to fade in, that is to increase the lens or diaphragm aperture from a fully closed setting to the proper setting for the given light, and to fade out, that is to close the aperture down from the appropriate setting for the given light to the fully closed position. This type of arrangement makes it possible, therefore, to start and end a particular filming sequence in a manner resembling that in professional motion pictures so that abrupt changes in scene are avoided. Cameras equipped with such a feature have a fade-out button that is separate from the above-mentioned trigger that serves to start the exposure of the film. Thus, the user actuates the fade-out button at the end of a scene and when he or she feels that fade-out sequence is over, the trigger is released.
Such an arrangement has the considerable disadvantage that the user cannot exactly ascertain when the fade-out sequence is completed and he or she cannot know exactly when to stop the film advance. Thus, at certain times film is wasted when the film advance is stopped too late, and at other times the fade out is not given time to complete. One attempt has been suggested to overcome this disadvantage by providing a timer in the device that automatically stops the film advance at the end of the fade-out sequence. Such an arrangement considerably reduces wastage of film, but nonetheless has the considerably disadvantage that it increases the cost of the camera and still does not exactly stop the film transport when the fade-out sequence is finished. A simple aging of the components, temperature, or other variables may cause the time constant of the stop circuit to become shorter or longer so that either film is wasted, or the fade-out sequence is not allowed to terminate completely.